Event-based multichannel direct link

ABSTRACT

Disclosed herein are exemplary techniques for the communication of information in a wireless system by using multiple wireless channels. A direct link between two or more wireless devices may be established by performing a direct link setup between two or more wireless devices using an access point, where the direct link setup is conducted over a base channel and the direct link is established on a parallel channel. The two or more wireless devices may switch to the parallel channel and use the established direct link to communicate information directly without the access point as an intermediary. In anticipation of a predetermined event, such as the transmission of a delivery traffic indication map (DTIM) beacon frame by the access point, the two or more wireless devices may switch back to the base channel so that uplink, downlink and/or peer-to-peer information may be transmitted and/or received.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/353,391 filed Jan. 29, 2003, now U.S. Pat. No. 6,791,962,issued Sep. 14, 2004, which also claims benefit of U.S. ProvisionalApplication No. 60/388,569, filed Jun. 12, 2002, entitled “Direct LinkProtocol In Wireless Local Area” and also claims benefit of U.S. patentapplication Ser. No. 60/515,701 filed Oct. 31, 2003 and entitled“Location Awareness in Wireless Networks,” the disclosures of which areherein incorporated by reference in their entireties.

The present invention is also related to U.S. patent application Ser.No. 10/880,367 filed concurrently herewith and entitled “Direct LinkRelay In a Wireless Network,” U.S. patent application Ser. No.10/880,367 filed concurrently herewith and entitled “Link MarginNotification Using Return Frame,” U.S. patent application Ser. No.10/880,325 filed concurrently herewith and entitled “Time-ScheduledMultichannel Direct Link,” all claiming benefit of U.S. ProvisionalApplication No. 60/515,701 filed Oct. 31, 2003, the entireties of whichare incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to wireless communicationsbetween wireless devices and more particularly to utilizing multiplewireless channels to communicate information.

BACKGROUND OF THE INVENTION

Various wireless standards, such as the Institute of Electrical andElectronics Engineers (IEEE) standards 802.11 a/b/c/e/g/i (referred tocollectively as IEEE 802.11), provide for wireless connectivity betweenwireless devices, such as, for example, between a wireless station andan access point connected to an infrastructure network. In conventionalwireless standards, the communication of information between peerwireless devices typically is routed through the access point. Toillustrate, to communicate information between a first wireless deviceand a second wireless device, the first wireless device wirelesslytransmits one or more frames of information to the access point, wherethe frames designate the second wireless device as their destination.The access point then modifies the headers of the frames and transmitsthem for reception by the second wireless device.

The process of using the access point as an intermediary has a number ofdrawbacks. For one, the communication of information is delayed byrouting it through the access point. Moreover, the wireless channel usedby the wireless devices and access point to communicate information(also referred to as the “base” channel) may be crowded with trafficfrom other wireless devices similarly seeking to transmit informationvia the access point. As a result, access contention mechanisms oftenare implemented, which typically results in additional delay.

Accordingly, an improved technique for communicating information betweenwireless devices would be advantageous.

SUMMARY OF THE INVENTION

The present invention mitigates or solves the above-identifiedlimitations in known solutions, as well as other unspecifieddeficiencies in known solutions. A number of advantages associated withthe present invention are readily evident to those skilled in the art,including economy of design and resources, transparent operation, costsavings, etc.

The present invention is directed to a method of communicatinginformation directly between the first and second wireless devices in awireless network including an access point logically connected to atleast a first wireless device and a second wireless device.

A further aspect of this invention is a method, in a wireless networkincluding an access point operably connected to at least a firstwireless device and a second wireless device, of providing informationbetween the access point and at least one of the first and secondwireless devices via a first channel for at least a portion of a firstperiod, providing a channel change request from the first wirelessdevice to the second wireless device on the first channel, providing anaffirmative response to the channel change request from the secondwireless device to the first wireless device on the first channel,switching the second wireless device to a second channel subsequent tothe receipt of the acknowledgement to the provision of the affirmativeresponse to the channel change request, switching the first wirelessdevice to the second channel subsequent to the transmission of theacknowledgement to the receipt of the affirmative response to thechannel change request; and communicating information directly betweenthe first and second wireless devices via the second channel for atleast a portion of a second period.

A further aspect of this invention is a wireless device, in a wirelessnetwork having an access point, including a transceiver, and a directlink module operably connected to the transceiver and adapted tofacilitate an establishment of a wireless direct link between thewireless device and another wireless device via a second channel,communicate information with the other wireless device via the wirelessdirect link for at least a portion of a first period, switch thetransceiver from the first channel to a second channel in anticipationof a predetermined event; and communicate information with the accesspoint via second channel for at least a portion of a second period.

A further aspect of this invention is a wireless system including anaccess point and at least a first wireless device and a second wirelessdevice. The first wireless device and a second wireless device areadapted to communicate information via a wireless direct link on a firstchannel during at least a portion of a first period, switch to a secondchannel in anticipation of a predetermined event; and communicateinformation with the access point on the second channel during at leasta portion of a second period.

Still further features and advantages of the present invention areidentified in the ensuing description, with reference to the drawingsidentified below.

BRIEF DESCRIPTION OF THE DRAWINGS

The purpose and advantages of the present invention will be apparent tothose of ordinary skill in the art from the following detaileddescription in conjunction with the appended drawings in which likereference characters are used to indicate like elements, and in which:

FIG. 1 is a schematic diagram illustrating an exemplary wireless systemhaving multiple channels for communicating information between wirelessdevices is illustrated in accordance with at least one embodiment of thepresent invention.

FIG. 2 is a chart illustrating an exemplary event-based channel switchprocess for the wireless devices of FIG. 1 in accordance with at leastone embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating an exemplary wireless devicein greater detail in accordance with at least one embodiment of thepresent invention.

FIG. 4 is a flow diagram illustrating an exemplary method forestablishing a wireless direct link on a parallel channel in accordancewith at least one embodiment of the present invention.

FIG. 5 is a flow diagram illustrating an exemplary event-based channelswitch process in accordance with at least one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is intended to convey a thorough understandingof the present invention by providing a number of specific embodimentsand details involving the communication of information using multiplewireless channels. It is understood, however, that the present inventionis not limited to these specific embodiments and details, which areexemplary only. It is further understood that one possessing ordinaryskill in the art, in light of known systems and methods, wouldappreciate the use of the invention for its intended purposes andbenefits in any number of alternative embodiments, depending uponspecific design and other needs.

For ease of illustration, the various techniques of the presentinvention are discussed below in the context of IEEE 802.11-basedwireless networking. However, those skilled in the art, using theteachings provided herein, may advantageously implement the disclosedtechniques in other wireless networks. Accordingly, reference totechniques and components specific to IEEE 802.11, such as an802.11-specific frame format or a series of transmissions specific to802.11, applies also to the equivalent technique or component in otherwireless network standards unless otherwise noted. Moreover, variousactions standard to IEEE 802.11 and other wireless standards, such as,for example, the transmission of an ACK frame to acknowledge receipt ofa frame, are omitted for ease of discussion.

Referring now to FIG. 1, an exemplary wireless system 100 employing oneor more exemplary event-based channel switching techniques disclosedherein is illustrated in accordance with at least one embodiment of thepresent invention. The system 100 incorporates a general wirelessnetwork topology described in IEEE 802.11 and other wireless standardswherein a plurality of wireless devices 102, 104 are associated with atleast one access point 106. The wireless devices 102, 104 includedevices enabled to communicate wirelessly using one or more protocols.Such protocols may include, for example, the IEEE 802.11 protocols(802.11a/b/e/g/i), ANSI, Hyperlan, etc. Examples of wireless devices mayinclude notebook (or “laptop”) computers, handheld computers, desktopcomputers, workstations, servers, portable digital assistants (PDAs),cellular phones, audio/visual (A/V) consoles, gaming consoles,televisions or other displays, etc. To illustrate, the system 100 mayinclude, for example, a multimedia system having one or more displays,audio/video components (e.g., a digital video disc (DVD) player or acompact disc (CD) player), sound systems, video game consoles, and thelike, where each of these components may be wirelessly connected to acentral console acting in the capacity of the access point 106.

The access point 106 may be connected to an infrastructure network 108or other network, such as, for example, the Internet, a local areanetwork (LAN), a wide area network (WAN), and the like. Thus, wirelessdevices 102, 104 may communicate with one or more networked devices onan infrastructure network via the access point 106. Moreover, thewireless devices 102, 104 may communicate with each other viaconventional wireless links 112, 114 with the access point 106 or, asdiscussed in greater detail below, via a wireless direct link 110between the wireless devices 102, 104 and optionally other wirelessdevices. Exemplary techniques for establishing and maintaining awireless direct link are described below and in U.S. patent applicationSer. No. 60/515,701, and U.S. patent application Ser. No. 60/388,569 theentirety of which is incorporated by reference herein.

In a conventional wireless network, information is communicated betweenwireless devices via an access point. A transmitting wireless devicetransmits the information to the access point on a base channel. Theaccess point then processes the information, such as by changing theheaders of one or more frames representing the information, and forwardsthe information to the receiving wireless device on the base channel.This use of the access point as the intermediary results in a delay inthe overall transmission time for the information, as well as crowds thebase channel because two transmissions take place, rather than one.Moreover, these transmissions may have been further delayed due tocongestion on the base channel by other transmitting devices.Furthermore, the distances to the access point may be much larger thanthe distance between the communicating devices, which allows thecommunicating devices to use much higher data rates on directcommunications.

Accordingly, the present invention provides techniques for enablingwireless devices to communicate information directly without use of theaccess point, while still permitting the transfer of information fromthe access point to the wireless devices, and vice versa. In at leastone embodiment, conventional wireless links 112, 114 between the accesspoint 106 and the wireless devices 102, 104, respectively, may be usedto initiate, establish and maintain a wireless direct link 110 betweenthe wireless devices 102, 104. The wireless direct link 110 preferablyis shifted to a parallel wireless channel (i.e., separate from the basechannel) so that the transmission of information via the direct link 110is not significantly impaired by traffic on the base channel, and viceversa.

Additionally, in at least one embodiment, the wireless devices 102, 104may be configured to switch back to the base channel or other wirelesschannel to receive buffered downlink information or peer-to-peerinformation from the access point 106 or to transmit uplink informationor peer-to-peer information to the access point 106, for example. Theswitch between the parallel channel and the base channel may occur inanticipation of a predetermined event, such as the periodic transmissionof a delivery traffic indication map (DTIM) beacon frame by the accesspoint 106, or the switch from the parallel channel to the base channel,or vice versa, may be initiated by either of the wireless devices 102,104.

Referring now to FIG. 2, a chart 200 depicting an exemplary event-basedchannel switching process is illustrated in accordance with at least oneembodiment of the present invention. The ordinate 202 of the chart 200represents time, whereas the abscissa 204 represents at least a portionof the frequency bandwidth in which the system 100 operates. In theillustrated example, base channel 206 represents the wireless channelused by the access point 106 to communicate with the wireless devices102, 104, and vice versa. Parallel channel 208 represents a channel usedby wireless devices 102, 104, to shift wireless direct link 110 to.

To illustrate, transmission period 210 may represent a direct linkhandshake period conducted on the base channel 206 to initiate andestablish the direct link 110 on the parallel channel 208 for directtransmission of information between the wireless devices. An exemplaryprocess for initiating and establishing a direct link 110 on a parallelchannel is described in greater detail below with reference to FIG. 4.The direct link 110 may be established on parallel channel 208 for anyof a variety of reasons, such as to reduce bandwidth congestion by usingmultiple channels to transmit information or to reduce latency in thetransmission of information between the wireless devices 102, 104. Afterestablishing the direct link 110 on parallel channel 208, the wirelessdevices 102, 104 switch to parallel channel 208 at or around time t₁.The subsequent transmission period 212 may represent a time periodwherein information may be communicated between the wireless devices102, 104 via the direct link 110 on parallel channel 208. To inform theaccess point about the temporary absence from the base channel, thewireless devices 102 and 104 transmit a frame to the access point withthe PM bit set, to indicate to the access point that they cannot bereached. In reality, the nodes are on the parallel channel and are mostlikely not in power save, but there is no difference from the viewpointof the access point because the wireless nodes cannot be reached ineither case. The access point will buffer traffic for these nodes inseparate power save queues, for later delivery.

Although the wireless devices 102, 104 may directly communicateinformation via the direct link 110 on parallel channel 208, thewireless devices 102, 104 may need to return to the base channel 206 oranother channel on a periodic basis in order to receive information fromthe access point 106 or other wireless device and/or to provide uplinkinformation to the access point 106 or peer wireless devices. Toillustrate, the wireless devices 102, 104 may be unable to receiveinformation from the access point 106 while their transceivers are tunedto the parallel channel 208 during transmission period 212. Accordingly,the access point 106 may buffer information intended for the wirelessdevices 102, 104 during the transmission period 212. As detailed in manywireless standards, access points typically periodically transmitinformation that indicates that the access point has bufferedinformation for one or more wireless devices associated with the accesspoint. For example, IEEE 802.11 provides for the periodic transmissionof a delivery traffic indication map (DTIM) beacon frame every DTIMperiod or at a target beacon transmission time (TBTT). The trafficindication map of the DTIM beacon frame indicates which wireless deviceshave information buffered at the access point.

Thus, in one embodiment, wireless devices 102, 104 switch back to thebase channel 206 in anticipation of a predetermined event 220(occurring, for example, at time t₂), where the predetermined event 220may include, for example: the transmission of buffered information,broadcast and/or multicast information by the access point 106 on thebase channel 206; the transmission of an indication of bufferedinformation by the access point 106, such as, for example, a DTIM beaconframe; and the like. In this instance, the wireless devices 102, 104 mayuse the indication of buffered information to determine whether theyhave information buffered at the access point 106 and then may requestthis information from the access point 106 using, for example, a PowerSave (PS)-Poll frame. Thus, the transmission period 214 may representthe transmission of multicast, broadcast, and buffered unicastinformation from the access point 106 to the wireless devices 102, 104,the transmission of uplink information from the wireless devices 102,104 to the access point 106, the transmission of peer-to-peerinformation between the wireless devices 102, 104 and other wirelessdevices, and the like.

At or about time t₃, the wireless devices 102, 104 may switch back toparallel channel 208 and continue communicating information directly viathe direct link 110 during transmission period 216. Alternatively, thewireless devices 102, 104 may initiate, establish and use a wirelessdirect link on a different channel. In either instance, the wirelessdevices 102, 104 may switch back to the base channel 206 in anticipationof another predetermined event 222, e.g., the transmission of anotherDTIM map, at or around time t₄. Once switched to the base channel 206,information between the access point 106, the wireless devices 102, 104and/or other wireless devices may be communicated as described aboveduring transmission period 218. The process of switching betweenchannels to alternatively transmit information over a direct link on onechannel and communicate with the access point 106 or other wirelessdevice on another channel may continue for any number of cycles asappropriate. Note that the direct link can always be used, irrespectiveof whether the wireless devices 102 and 104 reside on the parallelchannel or on the base channel.

Referring now to FIGS. 3-5, an exemplary configuration for wirelessdevices 102, 104 (illustrated as wireless device 302), as well asexemplary methods 400 and 500 of its operation are illustrated inaccordance with at least one embodiment of the present invention.Although certain actions are attributed to either wireless device 102 orwireless device 104 for ease of reference, those skilled in the art willappreciate that some or all of these actions may be performed by eitherwireless device 102 or wireless device 104.

In the illustrated example of FIG. 3, the wireless device 302(representative of either wireless device 102 or 104) includes at leasta transceiver 304 for transmitting and/or receiving signals representinginformation, one or more processors 306 and protocol stacks 308 forprocessing and otherwise preparing information for transmission via thetransceiver 304, as well as for processing information received via thetransceiver 304. The wireless device 302 further may include a multiplechannel direct link (MCDL) module 310 for initiating, establishing, andmaintaining a one or more wireless direct links on one or more channels,communicating information via the one or more wireless direct links,switching between channels as appropriate, and other various actionsdescribed in detail herein. The MCDL module 310 may be implemented assoftware, hardware, firmware, or a combination thereof. To illustrate,the MCDL module 310 may be implemented as a software component of theprotocol stack 308, as a separate software program or module executed bythe processor 306, or as a software or hardware component implemented aspart of the transceiver 304.

Referring now to FIG. 4, an exemplary method 400 for initiating andestablishing a wireless direct link on a separate channel is illustratedin accordance with at least one embodiment of the present invention. Toinitiate a direct link on a channel other than the base channel used bythe AP 106, one of the wireless devices 102, 104 (device 102 in thisexample) may transmit a setup request frame to the access point 106 onthe base channel for forwarding to the wireless device 104 at step 402,where the setup request frame represents an invitation or proposal toestablish a direct link on another channel. To this end, the setuprequest frame may include a channel information element (CIE) (e.g., inthe payload of the frame), where the CIE may include one or moreindicators associated with a proposed channel, such as, for example, thecenter frequency and channel width of the proposed channel or a lowfrequency and a high frequency of the proposed channel. The proposedchannel may be selected at random, or, in one embodiment, the wirelessdevice 102 may scan one or more potential channels for traffic andselect a channel having relatively little or no traffic as the proposedchannel.

The setup request may be encapsulated inside a regular data frame, usingLLC encapsulation. This method is described in more detail in U.S.patent application Ser. No. 60/515,701, which has been referencedbefore. Security credentials may also be included inside the setupframes. Due to the encapsulation in a regular data frame, any accesspoint will forward the frame to the ultimate destination withoutprocessing the data portion, irrespective of whether the access pointknows about this protocol or not. The LLC encapsulation effectivelycreates a transparent tunnel through the access point.

The access point 106 may process the setup request frame as necessaryand forward the setup request frame to the wireless device 104 at step404. Access points will usually forward this data frame withoutadditional processing of the payload. Upon receipt of the setup requestframe, the wireless device 104 may consider the proposal to establish adirect link on the proposed channel. If acceptable, the wireless device104 may transmit an affirmative setup response frame to the access point106 on the base channel for forwarding to the wireless device 102 atstep 406. If the proposal to establish a direct link is acceptable butthe proposed channel is not (because, for example, the wireless device104 cannot operate at the proposed frequency), the wireless device 104may transmit a conditional setup response frame to the access point 106on the base channel for forwarding to the wireless device 102. Theconditional setup response frame may include a proposal for an alternatechannel for consideration by the wireless device 102.

If the proposal to establish a direct link is unacceptable (e.g., thewireless device 104 does not have a multiple channel direct linkcapability), the wireless device 104 may transmit a negative setupresponse frame to the wireless device 102 indicating that the wirelessdevice 104 has declined to participate in a direct link with thewireless device 102. In this instance, the wireless device 102 mayattempt to set up a direct link 110 on the base channel or it may ceaseattempts to establish a direct link 110 with the wireless device 104. Inat least one embodiment, the setup response frame includes anagreed/denied/conditional field that may be used to indicate whether thesetup response is affirmative, negative or conditional. If theresponding device does not support direct link, it may not recognize themulti channel capability (i.e. the CIE element), and it may respond witha response message that does not include a multi channel capabilityelement (i.e. the CIE element). In this way, a direct link may still beset up, but possibly without the option of being shifted to anotherchannel.

If the setup response frame is affirmative or conditional, the setupresponse frame may further include an indication that the wirelessdevice 104 is entering a sleep mode or power-saving mode whereby theaccess point 106 is to buffer all information intended for the wirelessdevice 104 until the access point 106 is polled for the bufferedinformation. The power-saving mode indicator may include, for example, apower management (PM) bit set or cleared in the header of the setupresponse frame. Upon receipt of the setup response frame, the accesspoint 106 preferably enacts the buffering mechanism if so directed bythe power-saving mode indicator and forwards the setup response frame tothe wireless device 102 at step 408.

If the setup response frame is an affirmative response, the wirelessdevice 102 may transmit a setup confirm frame to the access point 106for forwarding at step 410. If the response is conditional uponacceptance of the use of the channel proposed by the wireless device104, the wireless device 102 may determine whether this proposed channelis acceptable. If so, the wireless device 102 may transmit the setupconfirm frame at step 410. If the response is negative, the wirelessdevice 102 preferably ceases any attempts to establish a direct link. Aswith the setup response frame, the setup confirmation frame may includean indication (e.g., a set PM bit) that the wireless device 102 isentering a sleep mode or power-saving mode and information intended forthe wireless device 102 should be buffered at the access point 106. Uponreceipt of the setup confirm frame, the access point 106 may activatethe buffering mechanism and forward the setup confirm frame to thewireless device 104 on the base channel at step 412.

Upon transmitting the setup confirm frame at step 410, in oneembodiment, the wireless device 102 switches its transceiver 304 to theagreed-to channel and waits for the arrival of the wireless device 104at step 414. Likewise, the wireless device 104 switches its transceiver304 to the proposed channel upon receipt of the setup confirm frame atstep 416. To announce its presence on the proposed channel, the wirelessdevice 104 may transmit an announcement frame on the proposed channeldirectly to the wireless device 102 at step 418. At this point, thedirect link 110 may be considered to be established and the wirelessdevices 102, 104 may initiate the communication of information on theparallel channel via the direct link 110 at step 420.

In another embodiment, devices 102 and/or 104 do not set the PM bit onthe direct link handshake frames, but separate frames with the PM bitset are transmitted instead. These frames may be Null frames or regulardata frames. Shifting the direct link to another channel is postponeduntil after the transmission of these separate PM frames. Shifting thedirect link may be accomplished by a permanent or temporary channelswitch, which are discussed in detail below. The direct link handshakemay still include a multi channel capability or a set of supportedchannels to which the direct link could be transferred.

There may be a delay between when the wireless device 102 switches tothe parallel channel and when the wireless device 104 switches. In oneembodiment, the wireless device 102 may use this waiting period to scanthe parallel channel to listen for traffic on the parallel channel. Thearrival of wireless device 104 may be announced by the transmission of afirst frame, which opens the direct link on the new channel. If the scanreveals that there is excessive traffic, the wireless device 102 maysuspend or cancel the direct link by transmitting, for example, a slowresumption mode (SRM) frame or a fast resumption mode (FRM) frame, orthe wireless device 104 may transmit a channel switch request to thewireless device 104 once the wireless device 104 has switched to theparallel channel, where the channel switch request represents a proposalto switch the direct link to another parallel channel. Permanent andtemporary channel switch requests are discussed in detail below.

During the direct link setup phase described above, peer-to-peer trafficthrough the access point is preferably is temporarily suspended to avoidany reordering of frames waiting at the access point 106. As notedabove, the wireless devices 102, 104 may use a power-saving modeindicator, such as, for example, the PM bit, to notify the access point106 that the devices 102, 104 are entering a power-save mode andtherefore directing the access point 106 to buffer downlink data untilit is requested from the wireless devices via, for example, powermode-poll (PM-Poll) frames as described by IEEE 802.11.

Referring now to FIG. 5, an exemplary event-based channel switch process500 is illustrated in accordance with at least one embodiment of thepresent invention. In the illustrated example, the method 500 initiatesat steps 502A and 502B wherein the wireless devices 102, 104 switch fromthe parallel channel (established using method 400 of FIG. 4, forexample) to the base channel of the access point 106 in anticipation of,or in preparation for, a predetermined event. In the illustratedexample, the predetermined event includes the transmission of a DTIMbeacon frame at steps 504A, 504B. As described above, DTIM beacon framestypically are transmitted substantially periodically (i.e., every DTIMbeacon interval) and include a bitmap that indicates which wirelessdevices have information buffered at the access point 106. Thus, itgenerally is desirable for the wireless devices 102, 104 to switch tothe base channel to receive the DTIM beacon frames so that the wirelessdevices 102, 104 may determine whether there is information waiting forthem at the access point 106. Accordingly, the wireless devices 102, 104preferably switch to the base channel slightly before the DTIM beacon isscheduled to be transmitted to help ensure that the wireless devices102, 104 are switched to the base channel in time to receive the DTIMbeacon frame. Moreover, the wireless devices 102, 104 may remain on thebase channel after receiving the DTIM beacon frame the transmission ofbroadcast and multicast information (steps 506A and 506B) typicallyfollows the transmission of a DTIM beacon frame.

In at least one embodiment, the wireless devices 102, 104 are configuredto switch back to the parallel channel at steps 508A and 508B afterreceiving the DTIM beacon frame and any multicast/broadcast information.If one or both of the wireless devices 102, 104 determine that they havebuffered information at the access point 106 using the DTIM beaconframe, the wireless device (device 102 in this example) may transmit apermanent channel switch (PCS) request frame on the parallel channelwith a request to switch back to the parallel channel to the otherwireless device at step 510. In this case, the PCS request framerepresents a request to switch to a proposed channel and includes one ormore indicators of the proposed channel, such as, for example, thecenter frequency and channel width or a low frequency and a highfrequency for the proposed channel. If the proposed channel switch isacceptable to the receiving wireless device (device 104 in thisexample), the receiving wireless device sends an affirmative PCSresponse frame on the parallel channel at step 512. If the proposedchannel switch is unacceptable (e.g., the receiving wireless devicecannot operate at the proposed frequency), the receiving wireless devicemay transmit a conditional PCS response frame having an alternateproposed channel or a negative PCS response frame if no alternatechannel is acceptable. If conditional, the wireless devices 102, 104negotiate an channel acceptable to both wireless devices 102, 104 or ifnegative, the wireless devices 102, 104 may cease communicating on theparallel channel and return to the base channel.

In another embodiment, a parallel channel may have been agreed uponduring the setup phase and the PCS request may not contain an explicitchannel information element. The receipt of a PCS request simplyindicates in that case that a switch to the other channel is requested,i.e. the parallel channel if transmitted on the base channel and thebase cannel if transmitted on the parallel channel.

In another embodiment, the wireless devices 102, 104 may stay on thebase channel after the end of the broadcast and multicast transmissions,while returning to the parallel channel is signaled by an explicit PCSrequest.

The PCS request and response frames preferably are transmitted asquality-of-service (QoS) frames having a piggybackcontention-free-acknowledgement (CF-Ack) as this type of frame typicallyrequires only a single transmission operation (TXOP). Examples ofsuitable piggyback frames that may be implemented as PCS request and/orresponse frames are described in detail in U.S. patent application Ser.No. 10/880,367 filed concurrently herewith and entitled “Link MarginNotification Using Return Frame.” Other frame formats, such asconventional data frames, may be used without departing from the spiritor the scope of the present invention.

Upon agreeing to a proposed switch to the base channel, the wirelessdevices 102, 104 make the channel switch at steps 514A, 514B. One orboth of the wireless devices 102, 104 then may request and receivebuffered information from the access point 106, provide uplinkinformation to the access point 106, and/or communicate information withpeer wireless devices via the base channel. To illustrate, the wirelessdevice 102 may use a reverse polling technique by transmitting a PS-Pollframe (e.g., a QoS+CF+Poll frame) to the access point 106 at step 516,where the PS-Poll frame represents a request for buffered informationand an indication (e.g., a clearing of the PM bit) that the wirelessdevice 102 has exited the power-saving mode. In response to the PS-Pollframe, the access point 106 may transmit buffered downlink informationto the wireless device 102 at step 518. After the wireless device 102has received the buffered downlink information (as indicated by theexpiration of an uplink or downlink timeout), the wireless device 102may transmit another frame, such as a null frame, to the access point106 at step 520, where the frame includes an indicator that the wirelessdevice 102 is entering the power-saving mode so that the access point106 may buffer any downlink information intended for the wireless device102. Uplink information and peer-to-peer information may be transmittedfrom the wireless devices 102, 104 in a similar manner.

To return to the parallel channel to resume communicating via the directlink 110, one of the wireless devices (device 102 in this example) maytransmit a PCS request frame on the base channel at step 522, where thePCS request frame may include an indication of the proposed channel towhich the wireless devices 102, 104 are to switch. Preferably, thewireless devices 102, 104 switch to the same parallel channel as before.However, it may be appropriate to switch to another channel because, forexample, the original parallel channel has become congested with trafficfrom other wireless devices or significant interference as appeared atone or more frequencies of the original parallel channel.

If the proposed channel is acceptable to the receiving wireless device(device 104 in this example) or if an alternate channel is to beproposed, the wireless device 104 may transmit an affirmative orconditional PCS response frame to the wireless device 102 on the basechannel at step 524. After agreeing to the channel switch, the wirelessdevices switch to the proposed parallel channel and recommence thecommunication of information between the wireless devices 102, 104 viathe direct link 110 on the parallel channel at step 528.

In addition or as an alternate to using a PCS sequence to switchchannels, the wireless devices 102, 104 may utilize a temporary channelswitch (TCS) sequence to temporarily move the direct link 110 to anotherchannel. The TCS sequence typically includes a TCS request frame thatmay include a CIE and a timing synchronization function (TSF) toindicate the time at which the direct link 110 is scheduled to return tothe current channel. The TCS sequence also may include a TCS responseframe that includes an agreed/denied/conditional field similar to thefield used for the PCS response frame. If the responding wireless devicecan not leave the current channel, for instance if it is not yet in apower-save mode with the access point 106, it may set the denied fieldinside the TCS response frame. Otherwise, if the responding wirelessdevice is ready to move to the proposed channel, it may set the agreedfield inside the TCS response frame.

The TCS sequence also may be used to temporarily move the direct link110 to the base channel for the exchange of information with the accesspoint 106 (e.g., buffered information) or with peer devices. The directlink 110 preferably remains active during this time, so that informationcan be exchanged via the direct link 110 on the base channel as well.Devices 102 and 104 should not leave the power save state with theaccess point during this temporary stay on the base channel (forinstance, by transmitting a frame to the access point with the PM bitreset), because it can not be ensured that they will be able to re-enterthe power save state prior to the scheduled departure to the parallelchannel with TCS.

Although the above techniques are described in the context of a directlink established between two devices, in some cases, multiple deviceseach may establish a direct link with a single device. The presence ofmultiple direct links raises the issue of selecting a common parallelchannel for the multiple direct links. In one embodiment, the wirelessdevice acting as the “hub” for the multiple peer devices may identify asuitable parallel channel that the multiple direct links may use by, forexample, proposing a parallel channel currently in use, by scanning oneor more other parallel channels, or by picking a channel at random.Another issue raised by multiple direct links includes channelswitching. In one embodiment, if a device having multiple direct linkswants to perform a channel switch, it preferably transmits a PCS requestframe to each of the other direct link peer devices before switching tothe proposed channel.

Yet another issue includes the implementation of power saving or thesleep mode. In one embodiment, this issue may be addressed by assumingthat the traffic pattern has a star topology, so that there is a centralnode that communicates with the peripheral nodes, but the peripheralnodes do not communicate with each other. Under this assumption, thecentral node may be treated as a constantly awake node (CAN) that actsas a surrogate access point by buffering information for all of theperipheral nodes, while maintaining a client association with the realaccess point at the same time. The peripheral nodes find can find thecentral node through its beacon transmissions and may associate with itinstead of with the access point. The peripheral nodes then may usereverse polling to retrieve buffered information, as described above.This solution is suited for applications like gaming and multimedia,where a single central node maintains connections with several remotenodes, like game controllers or actuators, respectively.

Other embodiments, uses, and advantages of the invention will beapparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein. Thespecification and drawings should be considered exemplary only, and thescope of the invention is accordingly intended to be limited only by thefollowing claims and equivalents thereof.

1. In an 802.11x wireless network comprising an access point logicallyconnected to at least a first wireless device and a second wirelessdevice, a A method of establishing a point-to-point connection directlybetween the a first wireless device and a second wireless devices devicecomprising: sending a setup request frame from the first wireless deviceto the second wireless device on a first communication channel via theaccess point, the setup request frame including a proposed secondcommunication channel; sending a setup response frame from the secondwireless device to the first wireless device on the first communicationchannel via the access point; and communicating information directlybetween the first and second wireless devices on the secondcommunication channel for a first time period.
 2. The method as in claim1, further comprising: switching the first and second wireless devicesfrom the second channel to the first channel in anticipation of apredetermined event; and communicating information between the accesspoint and at least one of the first and second wireless devices via thefirst channel for at least a portion of a second time period.
 3. Themethod as in claim 2, further comprising: switching the first and secondwireless devices from the second channel to the first channel prior tothe second time period.
 4. The method as in claim 2, further comprising:switching the first and second wireless devices from the second channelto a third channel; and communicating, for a third time period,information directly between the first and second wireless devices thesecond channel.
 5. The method as in claim 4, wherein switching thewireless devices to the third channel comprises: providing a setupconfirmation from the first wireless device to the second wirelessdevice via the access point, the setup confirmation confirming thesuitability of a wireless direct link on the third channel; switchingthe first wireless device to the third channel subsequent to thetransmission of the setup confirmation; and switching the secondwireless device to the third channel subsequent to the receipt of thesetup confirmation.
 6. The method as in claim 5, wherein establishingthe second wireless direct link on the third channel comprises:providing, on the second channel, a setup request from the firstwireless device to the second wireless device via the access point, thesetup request including one or more identifiers of the third channel;and providing, on the second channel, an affirmative setup response fromthe second wireless device to the second wireless device via the accesspoint in response to a receipt of the setup request at the seconddevice; wherein the setup confirmation is provided in response to areceipt of the affirmative setup response at the first wireless device.7. The method as in claim 6, wherein the one or more identifiers of thethird channel includes a center frequency and a channel width.
 8. Themethod as in claim 7, further comprising: scanning at least one channelto identify an unused channel, the unused channel being selected as thethird channel.
 9. The method as in claim 7, further comprising: randomlyselecting one of a plurality of channels as the third channel.
 10. Themethod as in claim 2, wherein the predetermined event includes asubstantially periodic event.
 11. The method as in claim 10, wherein thepredetermined event includes a periodic transmission of an indication ofinformation buffered at the access point, wherein at least a portion ofthe buffered information is intended for receipt by at least one of thefirst and second wireless devices.
 12. The method as in claim 11,wherein the indication from the access point includes a delivery trafficindication map (TIM) beacon frame.
 13. The method as in claim 10,wherein the predetermined event includes the delivery of broadcast andmulticast data.
 14. The method as in claim 1, wherein the second channelincludes a base channel for communicating information between the accesspoint to at least the first and second wireless devices.
 15. In an802.11x wireless network comprising an access point operably connectedto at least a first wireless device and a second wireless device, a Amethod of establishing a direct point-to-point connection between thetwo wireless devices comprising: providing information between the anaccess point and at least one of the a first wireless device and asecond wireless devices device via a first channel for at least aportion of a first period; providing a channel change request from thefirst wireless device to the second wireless device on the firstchannel; providing an affirmative response to the channel change requestfrom the second wireless device to the first wireless device on thefirst channel; switching the second wireless device to a second channelsubsequent to the receipt of the acknowledgement to the provision of theaffirmative response to the channel change request; switching the firstwireless device to the second channel subsequent to the transmission ofthe acknowledgement to the receipt of the affirmative response to thechannel change request; and communicating information directly betweenthe first and second wireless devices via the second channel for atleast a portion of a second period, wherein the 802.11x wireless networkaccess point is configured to facilitate communications in an 802.11xprotocol, and wherein the first channel is different than the secondchannel.
 16. The method as in claim 15, wherein the channel changerequest includes an indication of a proposed center frequency andchannel width for the second channel and wherein the affirmativeresponse to the channel change request includes an affirmation of theproposed center frequency and channel width for the second channel. 17.The method as in claim 15, wherein the information communicated duringat least a portion of the second period includes information buffered atthe access point during the first period and having at least one of thefirst and second wireless devices as an intended recipient.
 18. Themethod as in claim 15, wherein the first and second wireless devicesswitch from the first channel to the second channel in anticipation of apredetermined event further comprising: switching the first wirelessdevice from the first channel to the second channel in anticipation of apredetermined event; and switching the second wireless device from thefirst channel to the second channel in anticipation of the predeterminedevent.
 19. The method as in claim 18, wherein the predetermined eventincludes a substantially periodic event.
 20. The method as in claim 19,wherein the predetermined event includes a periodic transmission of anindication of information buffered at the access point, wherein at leasta portion of the buffered information is intended for receipt by atleast one of the first and second wireless devices.
 21. The method as inclaim 20, wherein the indication from the access point includes adelivery traffic indication map (TIM) frame.
 22. In a wireless networkhaving an access point, at least one A wireless device comprising: atransceiver; and a direct link module operably connected to thetransceiver and configured to: facilitate an establishment of a wirelessdirect link between the wireless device and another wireless device onthe network via a second frequency channel; communicate information withthe other wireless device via the wireless direct link on the secondfrequency channel for at least a portion of a first period; switch thetransceiver from the second frequency channel to a base channel inanticipation of a predetermined event; and communicate information withthe an access point via the base channel for at least a portion of asecond period, wherein the second frequency channel is different thanthe base channel.
 23. The wireless device as in claim 22, wherein thedirect link module is adapted to facilitate the establishment of thewireless direct link by: providing a channel setup request to the otherwireless device via the access point and the base channel; receiving anaffirmative response to the setup request from the other wireless devicevia the base channel; providing a setup confirmation to the otherwireless device via the base channel; and tuning the transceiver to thesecond channel subsequent to the provision of the setup confirmation.24. The wireless device as in claim 23, wherein the setup requestincludes an indication of a proposed center frequency and channel widthfor the second channel.
 25. The wireless device as in claim 22, whereinthe direct link module is adapted to facilitate the establishment of thewireless direct link by: receiving a channel setup request from theother wireless device via the access point and the base channel;providing an affirmative response to the setup request to the otherwireless device via the base channel; receiving a setup confirmationfrom the other wireless device via the base channel; and tuning thetransceiver to the second channel subsequent to the receipt of the setupconfirmation.
 26. The wireless device as in claim 25, wherein the setuprequest includes an indication of a proposed center frequency andchannel width for the second channel.
 27. The wireless device as inclaim 26, wherein the direct link module is adapted to facilitate theestablishment of the wireless direct link by: providing a channel changerequest to the other wireless device via the access point; receiving anaffirmative response to the channel request from the other wirelessdevice via the access point; tuning the transceiver to the secondchannel subsequent to the receipt of the affirmative response.
 28. Thewireless device as in claim 22, wherein the direct link module isadapted to facilitate the establishment of the wireless direct link by:receiving a channel change request from the other wireless device viathe access point; providing an affirmative response to the channelrequest to the other wireless device via the access point; and tuningthe transceiver to the second channel subsequent to the provision of theaffirmative response.
 29. The wireless device as in claim 22, whereinthe predetermined event includes a substantially periodic event.
 30. Thewireless device as in claim 29, wherein the predetermined event includesa periodic transmission of an indication of information buffered at theaccess point during the first period, wherein at least a portion of thebuffered information is intended for receipt by at least one of thefirst and second wireless devices.
 31. The wireless device as in claim30, wherein the indication from the access point includes a deliverytraffic indication map (TIM) frame.
 32. The wireless device as in claim22, further comprising: at least one processor; and wherein the directlink module includes executable instructions adapted to manipulate theprocessor to: facilitate the establishment of the wireless direct link;communicate information with the other wireless device via the wirelessdirect link; switch the transceiver from the first channel to the basechannel in anticipation of the predetermined event; and communicateinformation with the access point via the wireless direct link on thebase channel.
 33. A wireless system comprising: an access point; and atleast a first wireless device and a second wireless device; wherein thefirst wireless device and the second wireless device are configured to:communicate information via a wireless direct link on a first channelduring at least a portion of a first period; switch to a second channelin anticipation of a predetermined event; and communicate informationwith the access point on the second channel during at least a portion ofa second period, wherein the first channel is different than the secondchannel.
 34. The wireless system as in claim 33, wherein thepredetermined event includes a substantially periodic event.
 35. Thewireless system as in claim 34, wherein the predetermined event includesa periodic transmission of an indication of information buffered at theaccess point during the first period, wherein at least a portion of thebuffered information is intended for receipt by at least one of thefirst and second wireless devices.
 36. The wireless system as in claim35, wherein the indication from the access point includes a deliverytraffic indication map (DTIM) frame.
 37. A wireless device comprising: atransceiver; and a direct link module operably connected to thetransceiver and configured to: provide a channel setup request toanother wireless device via an access point (AP) on a base frequencychannel of the AP; receive an affirmative response to the setup requestfrom the another wireless device via the AP on the base frequencychannel; provide a setup confirmation to the another wireless device viathe AP on the base frequency channel; and tune the transceiver to asecond frequency channel after providing the setup confirmation, whereinthe second frequency channel is different than the base frequencychannel.
 38. The wireless device of claim 37, wherein the setupconfirmation includes power management information that, when decoded bythe AP, instructs the AP to begin buffering packets destined for thewireless device.
 39. The wireless device of claim 37, wherein the directlink module is further configured to, after tuning the transceiver tothe second frequency channel, and prior to receiving an announcementframe from the another wireless device on the second frequency channel,scan the second frequency channel to determine a traffic level, and ifexcessive traffic is found, transmitting a frame suspending or cancelingthe direct link.
 40. The wireless device of claim 37, wherein thechannel setup request provided to the another wireless device via the APis encapsulated inside a data frame using LLC encapsulation.
 41. Thewireless device of claim 37, wherein the direct link module is furtherconfigured to switch the transceiver from the second frequency channelto the base frequency channel in anticipation of a predetermined event.42. The wireless device of claim 41, wherein the direct link module isfurther configured to, after switching the transceiver from the secondfrequency channel to the base frequency channel in anticipation of apredetermined event, receive buffered packets from the AP on the basefrequency channel.
 43. The wireless device of claim 41, wherein thedirect link module is further configured to, after switching thetransceiver from the second frequency channel to the base frequencychannel in anticipation of a predetermined event, receive a deliverytraffic indication map (DTIM) beacon frame from the AP on the basefrequency channel.
 44. The wireless device of claim 41, wherein thepredetermined event is a substantially periodic event.
 45. A wirelessdevice comprising: a transceiver; and a direct link module operablyconnected to the transceiver and configured to: receive a channel setuprequest from another wireless device via an access point (AP) on a basechannel of the AP; provide an affirmative response to the channel setuprequest to the another wireless device via the AP on the base channel;receive a setup confirmation from the another wireless device via the APon the base channel; and tune the transceiver to a second channelresponsive to the receipt of the setup confirmation, wherein the secondchannel is different than the base channel.
 46. The wireless device ofclaim 38, wherein the affirmative response includes power managementinformation that, when decoded by the AP, instructs the AP to beginbuffering packets destined for the wireless device.
 47. The wirelessdevice of claim 38, wherein the direct link module is further configuredto, after tuning the transceiver to the second channel, transmit anannouncement frame to the another wireless device on the second channel.48. A method of linking a first wireless device with a second wirelessdevice comprising: providing a channel setup request from the firstwireless device to the second wireless device via an access point (AP)on a base channel of the AP; receiving at the first wireless device anaffirmative response to the channel setup request from the secondwireless device via the AP on the base channel; providing a setupconfirmation from the first wireless device to the second wirelessdevice via the AP on the base channel; tuning the transceiver of thefirst wireless device to a second channel after providing the setupconfirmation, wherein the second channel is different than the basechannel; and communicating with the second wireless device over thesecond channel.
 49. A method of linking a first wireless device with asecond wireless device comprising: receiving a channel setup request atthe first wireless device from the second wireless device via an accesspoint (AP) on a base channel of the AP; providing an affirmativeresponse to the channel setup request from the first wireless device tothe second wireless device via the AP on the base channel; receiving asetup confirmation at the first wireless device from the second wirelessdevice via the AP on the base channel; tuning the transceiver to asecond channel responsive to the receipt of the setup confirmation,wherein the second channel is different than the base channel; andcommunicating with the second wireless device over the second channel.